AIRFLO MITE de Ron Warring. 1948. USA

Publicado en Model Aviation Plan Book 1948

Proj Span inch 32.00

THE original Airflo Baby was produced as a kit design on American lines. That is to say, although featuring a cabin layout, the appearance was still definitely American, with deep, narrow fuselage and polyhedral wing.

Designed around the Mills diesel the prototype BABY proved to be the ideal sports flier. Constructional simplicity was the aim, both from the point of view of making the kit list as straightforward as possible and from the modeller's viewpoint in requiring the least time on the building board. The Airflo Baby was designed to fly—not to absorb hours of building time.

The original prototype proved to be quite a duration job and used to float around almost indefinitely if there were any signs of lift about. The second prototype showed up a rather peculiar feature—but one, incidentally, which never detracted from its performance. Trimmed for a near vertical climb the tail would waggle from side to side, but it never got into trouble on this score. We found two cures. Speeding the model up stopped the tail wag immediately, and this was accomplished by either flattening out the climb slightly or increasing the speed of the motor by fitting a slightly smaller prop. A three inch strip of 1/2 in. by 1/8 in. balsa cemented to the fin edge at right angles also removed these peculiar symptoms.

But in the end we went back to the original set-up to make the flight more interesting. On the very next attempt the job found a modest riser and continued up. . . and up. . . and up. .. So we never did find out anything more about tail-wagging on this ship, and the third one we flew behaved as sedately as any other good model.

Around Christmas, 1946, we had paid a visit to J. Colyer of Majesco Miniature Motors—then at Littlehampton when he had just finished the first prototype of the Majesco Mite •75 c.c. diesel. Colyer had it fitted in a straightforward 200 sq. inch job which weighed about 8 ounces and this we flew and flew all one winter's afternoon. Which gave rise to the thought that here indeed was the ideal sports model—something really small and robust. All there was to do was fill the tank, flip the prop (at least Colyer did—we needed more than several flips to get the motor going)—and fly.

Soon afterward the Airflo Baby was scaled down to a size to take a diesel of around • 75 c.c. But at that time there just were not any motors of this size available on the market. The prototype had odd flips on a most amazing variety of motors, often with ballast at "strategic points" to bring the C.G. out somewhere near where we knew it ought to be.

It took it all—and- then the design went on the shelf until suitable motors made the commercial market. As soon as the Amco was announced we concluded this was just the job. Quite high power for a model of this size-its climbing angle is greater than that of the Airflo Baby with a Mills—but light enough to keep loading right down and reduce that "rate of sink" when the power cuts.

Just a few mods. to the nose end and the Amco was installed. The happy inspiration of cutting a hole in the windscreen so that you can reach the intake tube to choke has paid dividends time and time again. And we never bothered to fit a timer to our job, but simply " guestimated " the power duration from the tank level before release. However, a timer link-up is very straightforward and is well worth the little extra trouble.

Constructional features are basically the same on the two Airflo models, although the Mite is probably the more rugged of the two.

The fuselage is built on the now familiar crutch principle--the crutch in this case being 3/16 square balsa. This is pinned out directly over a full-size drawing and cemented. Note how the hardwood bearers are shaped and cemented in with the crutch.

All formers are then cut from - sheet stock and cemented at their respective stations on the crutch. Wing platform and keel stringers virtually complete the fuselage assembly.

The 16 s.w.g. undercarriage is first bent to shape and then bound and cemented to the hardwood crutch members. Hardwood wheels are recommended on account of their durability and relatively light weight. These should be of streamlined section; balloon-type wheels only add unnecessary drag.

Wing ribs and tip pieces are cut from sheet. These are given full size and only require tracing or marking off on to sheet of the correct thickness. Either place a sheet of carbon paper over the balsa, lay under plan and draw round outline with a pencil; or lay wood under plan and prick around outline with a pin. We recommend the former method.

By shaping the spar ends before assembly the wing can be built in one piece flat over a full size drawing. When set, simply set up at correct dihedral angles and add spar braces.

Note that the centre rib is cut from 1/2in. by 1/8 in. strip stock and then shaped to correct contour after this stage in construction.

Sand down structure, particularly the tips, and then cement leading edge sheeting in place. This sheeting must be cemented to each rib as well as leading edge and spar, otherwise it will cockle when water-sprayed and doped.

The tailplane is very simple--and very light. Cut the ribs and tip pieces carefully, so that everything fits accurately. The spar must be tapered before assembly as shown. The fin is even simpler, the outline cut from pieces of sheet and scrap strip used for the two " ribs " Section is flat plate.

Tissue is used to cover all surfaces. Pin down after water spraying to avoid warping---and again after doping. We strongly recommend that after doping all surfaces be left pinned or weighted down for at least 24 hours.

The fuselage can be single or double tissue covered. Silkspan or thin silk is much better if obtainable. Three or four coats of dope on the fuselage, two on the wings, and one on the tail surfaces are adequate.

Smaller motors like the Ace .5 c.c. give very pleasing flights—still hot enough for the average enthusiast. Putting in larger motors—around 1 c.c. —will certainly give you climb, but it works out a bit hard on glide with all that extra weight hung out front.

A few hand launches with propeller removed should soon give you glide trim. Add incidence to the wing to cure diving tendency and positive to the tail to cure stall (positive means packing up the leading edge---but only 3/16" at a time). A very slight touch of rudder—right or left—will give a circle on the glide.

Then get the motor revving—and launch! If there are any signs of instability, suspect warps and check accordingly. Stalling under power should not occur—unless the tailplane has been given negative incidence---but, if persistent, can be cured by tilting the motor slightly downwards through shims inserted under rear of mounting lugs.

Follow American practice if you intend to make sidethrust adjustments. Make the bolt holes oversize and simply slacken off nuts and twist motor to setting required; then tighten down securely again. Use lock nuts, where obtainable. Plain nuts have an annoying habit of working loose and becoming lost on the flying field.